1. Field of the Invention
The present invention relates to stepping exercisers, and more particularly to a stepping exerciser which comprises a step plates link motion mechanism to effectively accurately force the two step plates to alternatively oscillate back and forth without causing mechanical sticking problem.
2. Description of the Prior Art
In the conventional structure of stepping exerciser, the two step plates for stepping are connected to alternatively oscillate up and down by a rope which is mounted on a rope pulley fastened in the machine frame at the top. Because the rope has a fixed length with its two opposite ends respectively secured to the two step plates of the stepping exerciser, when a first step plate is stepped downward, the other step plate is simultaneously pulled by the rope to lift. This structure is not practical in use, because of the following disadvantages:
1. Because the rope to link the two step plates has somewhat a resilient property which causes the step plates to vibrate when they are alternatively moved to the upper or lower limit. Because of the vibration problem of the step plates during operation, step instability may occur.
2. Because the two step plates are linked by the rope to alternatively oscillate up and down, they tend to simultaneously move up or down during operation, or the rope may disengage from the rope pulley easily to obstruct the operation.
In U.S. Pat. No. 4,934,690 there is disclosed an exercising machine for use in the standing position, which has means to effectively eliminate shock waves from the two levers (step plates) during stepping exercises. In this structure of exercising machine, a rod is fastened at the bottom of the machine frame and respectively connected to the two levers by two rocker arms. During operation, as shown in FIG. 1, the two opposite ends of the rod 1 are alternatively oscillated up and down. However, because the lower joint 21 of each rocker arm 2 is carried by the rod 1 to move left and right while the upper joint 22 is confined to oscillate back and forth, the rocker arms 2 may be distorted during operation of the machine. Referring to FIG. 2, when the levers 3 are alternatively stepped to move up and down through a circular track, the upper joint 22 of each rocker arm 2 is simultaneously carried to oscillate back and forth. However, because the lower joint 21 of each rocker arm 2 is confined to oscillate left and right, the rocker arms 2 may be distorted easily.